What is the encoding used in encode function with escape in postgres? - sql

Question

I've a bytea stored in the database , I'm trying to convert it to string via the encode function and it works :
select encode(blobvalue,'escape') from myTable ;
However the following is failing :
select convert_from(blobvalue,'UTF8') from myTable ;
ERROR: invalid byte sequence for encoding "UTF8": 0xac
my server encoding is UTF8:
SHOW SERVER_ENCODING;
server_encoding
-----------------
UTF8
(1 row)
any explanation why the encode is working but the convert_from not ? isn't the encoding used in encode with escape same as server encoding ?

Answer 1

encode() will only convert ASCII bytes to characters. Everything else will be an escaped octal value:
SELECT encode('\x4142AC43', 'escape');
encode
═════════
AB\254C
(1 row)
Here, the byte 0xAC is not an ASCII character and is rendered as \254.
convert_from(), on the other hand, considers the bytea as a string in a certain encoding and will fail if it finds bytes that are not correct:
SELECT convert_from('\x4142AC43', 'UTF8');
ERROR: invalid byte sequence for encoding "UTF8": 0xac
So you have to figure out in which encoding your bytea value actually is.